Climbing with microbes: How elevation shapes the bacterial root microbiome of wild grapevine and selects plant growth-promoting hubs for sustainable viticulture.

Climate change is challenging agriculture and food security due to the limited adaptability of domesticated crops. While plant range shifts along latitudinal and altitudinal gradients are well-documented, their impacts on belowground microbial communities and plant adaptability remain poorly understood. Vitis vinifera subsp. sylvestris, the wild ancestor of cultivated grapevine, is an endangered Mediterranean species whose microbial interactions are key for biodiversity conservation and sustainable viticulture. We investigated how elevation shapes bacterial communities in the rhizosphere and root endosphere of V. sylvestris across increased elevational gradient. Using soil physicochemical analysis and 16S rRNA sequencing, we found contrasting diversity trends: rhizosphere richness decreased with elevation, while endosphere richness increased. Proteobacteria dominated both compartments, but Actinobacteria, Bacteroidetes, and Acidobacteriota shifted along elevation gradients. Bacteroidetes and Verrucomicrobiota increased at high elevations, while Alphaproteobacteria declined. Elevation also lowered soil pH, phosphorus, and potassium but increased organic matter and water content. Structural equation modeling showed elevation reduced rhizosphere diversity through soil degradation, whereas in the endosphere, it directly boosted diversity by selecting stress-adapted taxa. Notably, mid-elevation sites hosted the most diverse and functionally enriched bacterial communities, including 40 potential plant growth-promoting species. Co-occurrence network analysis identified elevation-specific keystone taxa critical for nitrogen fixation, phosphate solubilization, and metabolite production. Functional predictions revealed shifts in KEGG pathways related to stress resilience. Our findings highlight the importance of elevation in shaping beneficial root microbiomes, offering a microbial roadmap for V. sylvestris conservation and climate-resilient viticulture.